Fe-MIL-88NH₂ Metal–Organic Framework Nanocubes Decorated with Pt Nanoparticles for the Detection of Salmonella

Early screening of Salmonella is of utmost importance to minimize the incidence of related foodborne diseases. Here, we reported an immunosensor to fast detect Salmonella using Fe-MIL-88NH2 metal–organic framework (Fe-MOF) nanocubes to load platinum nanoparticles (PtNPs) for signal amplification and smartphone thermal imaging to monitor the temperature change. The Fe-MOF nanocubes decorated with PtNPs (Fe-MOF/PtNPs) were prepared as peroxidase mimics to catalyze hydrogen peroxide (H2O2) to produce O2. The immune magnetic nanoparticles (MNPs), the target bacteria, and the immune Fe-MOF/PtNPs were first mixed by the three-dimensional (3D) chaotic micromixer and conjugated in the microfluidic chip to form MNP–bacteria–Fe-MOF/PtNPs sandwich complexes. After magnetic separation and washing, H2O2 was injected and decomposed by Fe-MOF/PtNPs on the sandwich complexes to generate O2 in a sealed chamber. The increase in the pressure pushed the preloaded water to react with calcium oxide powder, resulting in the generation of heat, which was measured using the smartphone-based thermal sensor to determine the bacteria. The microfluidic immunosensor could detect Salmonella as low as 93 CFU/mL within 1 h.